Data Sheet TTC XPDR-520 Radar Enhancing C-Band Transponder Data Sheet Download Resource Login to download this resource Username Enter your Curtiss-Wright Defense Solutions username. Password Enter the password that accompanies your username. Forgot password? Don’t have an account? Register here. The XPDR-520 series are C-band transponders that are used primarily to augment and enhance the tracking capabilities of C-band ground radars.